Sollae Systems CSE-H55N, Руководство пользователя

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CSE-H55N User
’
s Manual Ver. 1.2
- 60 -
http://www.ezTCP.com
network to make differential voltage within the standard. (BR1 and BR2 are biasing resistors
in the above picture)
In normal case, RS485 line drivers don’t require any biasing resistors, but it makes some
problems in some cases.
Generally 680 ohm resistors are used for the biasing resistors. If the biasing resistor is
higher, power consumption is lower but delay is longer. And if the biasing resistor is lower,
delay might is shorter but power consumption will be higher.
9.2.3 Termination Resistors
There should be two termination resistors in the ends of transmission line to prevent
reflection waves when the cable is long or communication speed is fast. (TR1 and TR2 are
termination resistors in the above picture.)
The resistors’ resistance should be same to cable’s characteristic impedance. Normal
cable’s characteristic impedance is 100 ohm or 120 ohm.
9.3 Configuring an RS422 Network
9.3.1 1:1 Configuration
The following is 1:1 configuration of RS422.
TRX+
TRX-
GND
RX+
RX-
GND
CSE-H55N
RX+
RX-
GND
TX+
TX-
USER DEVICE
TR1
B
R
1
5V BR2 TR2
Figure 9-2 RS422 1:1 Configuration
9.3.2 1:N Configuration
The following is 1:N configuration of RS422.
When the CSE-H55N operates as RS422 mode, it can’t be a slave because its driver is
driving always.